1. Field of the Invention
The present invention relates to production control methods and systems for automated production lines such as automated assembly lines for automobiles, and more particularly, to production control methods and systems with improvement in ensuring the conversion of data related to the contents of processing at each process, and in increasing the processing speeds.
2. Background Art
In an automated production line, automated processing units such as working units and assembling units are disposed at necessary positions in the production lines to process objects to be processed (OBJs) with necessary processing. The automated processing units (APUs) apply various processing to the OBJs which are moving toward the station along the production lines.
In a case in which different models or kinds of products are to be produced in a single production line, as is often the case with different car models produced in an automobile production line, different processing are required in accordance with each model. For example, in a conventional automobile production line, workers enter instruction data in each corresponding APU, indicating car models and other information. Such instruction data includes various data indicating car models, discrimination by number of doors such as between 2-door and 4-door models, and optional parts, if any, to be incorporated in the model, and the like. Instruction data to be entered is determined by the workers' visual observation of an identification card attached to the car being produced.
When the instruction data is entered, the APU generates a code for determining an operation to be conducted by utilizing a conversion table stored in its interior memory and applies a processing to the car being produced in accordance with this code. For example, in the case of an APU for automatically attaching windshields, the APU generates a code in accordance with the car model based on the instruction data, retrieves a windshield fitting the car model from a storage station, based on the code, and attaches the windshield to a specified position on the car.
However, the conventional production lines described above have problems as follows:
(1) a misdetermination of instruction data tends to occur since the instruction data is identified by the worker's visual observation; correcting the result from the misdetermination takes time, and the productivity of the production line thereby decreases; PA1 (2) entering instruction data consumes time since the entering is done manually by the worker, thereby further decreasing productivity; and PA1 (3) changes in instruction data such as car model requires subsequent changes in every and all APUs, since each APU is equipped with its own respective conversion table, and the related adjustments are thereby complicated. PA1 I. a huge storage capacity is required if sufficient information is to be stored for controlling all the operations to be conducted by the APU; and PA1 II. specifications for processing to be processed by an APU cannot be established until the OBJ has been brought in the APU and the necessary information has been read from the ID plate attached to the OBJ, since the ID plate is transported together with the OBJ, whereby the APU is caused to be idle until a next OBJ arrives to the APU after the processing of the current OBJ is completed.
In order to overcome these problems, a data entering method may be considered in which an information storage medium for storing instruction data in memory (hereinafter referred to as an "ID plate") is attached to each OBJ so that the APU reads and enters information therein automatically; instead of the data being entered by a worker, the instruction data is stored in the ID plate attached to the OBJ, and by reading this ID plate, the APU applies processing to the OBJ in accordance with the entered data.
However, when the information is stored in such a storage medium, problems tend to arise as follows: